Sirup treatment of apples



United States Patent O SIRUP TREATMENT OF APPLES Dante G. Guadagni,Albany, Califl, assignor to United States of America as represented bythe Secretary of Agriculture No Drawing. Application September 29, 1950,Serial No. 187,654

3 Claims. (Cl. 99193) (Granted under Title 35, U. S. Code (1952), see.266) This application is made under the act of March 3, 1883, as amendedby the act of April 30, 1928, and the invention herein described andclaimed if patented in any country, may be manufactured and used by orfor the Government of the United States of America throughout the worldfor governmental purposes without the payment to me of any royaltythereon.

This application is a continuation-in-part of my prior application forpatent Serial No. 791,441, filed December 12, 1947, now abandoned.

This invention relates to the treatment of apples, particularly to thetreatment of apples with sugar solutions to improve the texture thereof.

Preservation of apples by freezing is well known and widely used, butseveral problems are encountered. One of the foremost is the fact thatmany types of apples such as Delicious, McIntosh, Gravenstein, etc. forma product of poor texture. When the frozen apples are thawed, they arefound to be soft and entirely unsuitable for use in making pies,cobblers, tarts, etc. In some cases, the thawed apples are firm intexture but become mushy when used in pies or other bakery products.

It has been found that if the apples are impregnated with sugar syrupprevious to freezing a vastly superior product is obtained. To this end,apples, preferably in the form of slices, are subjected to a vacuum toremove a large proportion of the air present in the apple tissues; thevacuum is then broken while the apples are in contact with sugar syrupwhereby they absorb the syrup. The slices are then drained to removeexcess syrup and frozen in the customary manner. Alternatively, theslices may be impregnated with syrup by dipping them in the sugar syrup,draining off the excess syrup, then placing the slices in cans, applyinga vacuum to exhaust the air from the apple tissues and to impregnate theslices with the syrup coated on their surfaces. The cans are then sealedWhile under vacuum and the product frozen in the customary manner. Whenthe frozen product is thawed, there is no loss in texture, but theapples are found to be of a firm, crisp texture, similar, and in somecases superior, to that of the fresh fruit. Further, the product issweet and has a pleasant, natural flavor and can be used directly as adessert or can be used in the preparation of pies, cobblers, tarts, etc.For the preparation of pics and other bakery products the applesprepared according to this invention are often superior to the freshfruit. Thus, for instance, if fresh Delicious apples are used to makepies, they will be somewhat soft in the finished product. On the otherhand, if Delicious apples are treated according to the instant inventionand then made into pies, they will have a firm texture in the finishedproduct. Another advantage to be mentioned is the amount of drain liquidobtained when the frozen fruit is thawed. When apples are frozen by theusual technique and then thawed, considerable liquid will drain out ofthe fruit. The formation of this drain liquid is consideredobjectionable by commercial users of frozen apples and it is thereforean important factor for control. When apples are prepared according tothis invention, frozen, and then thawed, the amount of drain liquid ismuch less than with the conventionally prepared apples.

Another point of departure is that in the usual freezing process theapples are first sulphited as by dipping into an aqueous solution ofsodium bisulphite. The apples must then be stored for about 8 to 12hours to allow the sulphite to penetrate and thus to obtain the maximumeffect against browning. In the instant process, no stor- 2,702,248Patented Feb. 15, 1955 age period is necessary after sulphiting. In thevacuum impregnation step the sulphite penetrates thoroughly into thefruit. Further, lower amounts of S02 are required. Whereas conventionalpractice will require at least 2000 to 3000 p. p. m. of S02, whenoperating according to this invention, the sulphiting solution cancontain but 10001500 p. p. m. of S02 and elfective results can beaccomplished with a one-minute dip. If, instead of a separate sulphitingdip, the sulphiting agent is incorporated in the syrup, even lowerconcentrations of S02 may be used.

An important feature of this invention is that the sugar syrupimpregnated apples are packaged and frozen as such and are not coveredwith sugar syrup or dry sugar. Thus after the vacuum impregnation step,the apples are drained and packaged in such condition then frozen. Inthe alternative procedure, the apples are dipped in the syrup, drainedand sealed in cans under vacuum. Thus in every case when operating inaccordance with this invention, the added sugar is within the appletissues and the exteriors of the slices are at most only covered with athin film or coating of sugar syrup. These factors have a very importanteifect in reducing the amount of liquid which exudes from the product onthawing. Thus the frozen products in accordance with this invention whenthawed exude only a minor amount of liquid on the order of 10% and muchless in some cases. Such result cannot be achieved with prior arttechniques. Thus it has been proposed that fruit be vacuum-impregnatedwith syrup and then packed in sugar syrup or dry sugar. In suchtechniques there is a large drainage loss on thawing. The point is thatin this prior method, the sugar surrounding the fuit extractsconsiderable moisture from the fruit tissues by osmosis. As a resultwhen the product is thawed, it exudes an amount of liquid over and abovethat added to cover the fruit since this exuded liquid contains both (1)the syrup used to cover the fruit plus (2) the moisture drawn out of thefruit by osmosis. A comparison of the instant process with that of theprior art is shown herein in Example 5. This example illustrates clearlyhow the instant process is superior with regard to amount of drainageliquid formed on thawing.

An object of this invention is to provide a process for the vacuumimpregnation of apples with sugar solution.

Another object of this invention is to provide a process for preparingfrozen apples, wherein the apples are first vacuum-impregnated withsugar solution.

Further objects and advantages will be obvious from the disclosureherein.

As heretofore stated, this invention involves the vacuum impregnation ofapples with sugar solution. Many types of apparatus can be utilized forthis procedure. One type of apparatus which has been found to givesatisfactory results is described as follows:

The impregnator vessel is a large glass jar equipped with a ground,flanged top. A glass lid provided with a valved port fits snugly on saidflanged top. By use of stopcock grease, or other suitable lubricant,this joint can be made vacuum tight. In performing the impregnation, theapples are placed in the jar and a heavy, pierced porcelain plate is puton top of them to hold them down. Syrup is then poured into the jar insuflicient quantity to cover the apples. The lid is then placed on thejar and the port on the lid connected with a suitable source of vacuumsuch as a vacuum pump. Preferably a vacuum gauge is put in the line tobe sure that the system is functioning properly. As soon as theatmosphere in the jar becomes ratified, intense frothing occurs as theair in the apple tissues is withdrawn. The vacuum treatment is continueduntil this bubbling ceases or at least becomes slow. The vacuum is thenbroken and the apples are permitted to remain in the syrup for a fewminutes so that impregnation can be effected. It is obvious that manydifferent types of apparatus can be utilized for this purpose. Thevessel may be made of stainless steel, for instance, and may be equippedwith sight glasses, inlet ports, drain pipes, etc.

It is not essential to have the apples immersed in the sugar syrupduring the vacuum treatment. The apples may be placed in a vessel whichis connected to a source of sugar syrup by a valve-controlled pipe. Thisvalve is closed and the vessel is subjected to vacuum. After thistreatment has been continued for a sufficient length of time, the valveis opened, whereby sugar syrup is drawn into the vessel and serves toimpregnate the apples. In such treatment the syrup is preferably heatedto obtain quicker impregnation.

If desired, further impregnation can be obtained as follows: The applesare subjected to vacuum, then contacted with sugar syrup to impregnatethe apple tissues. Pressure is then applied to the apples immersed inthe sugar syrup, whereby further impregnation of the syrup is effected.

In the alternative modification of the process of this invention, theapples, preferably in the form of slices, are immersed in the sugarsyrup or otherwise treated so that they are uniformly coated with thesyrup. Any excess syrup is removed by draining and the syrup coatedapples are placed in cans or other vessels which may be hermeticallysealed. Vacuum is then applied to the cans whereby to remove the gasesfrom the apple tissue and to cause the syrup coating to enter into thetissue into the voids formerly occupied by the gases. The cans are thensealed while under vacuum.

The following examples describe particular steps, conditions, andmaterials in accordance with this inven; tion. These examples aresubmitted only by way of illustration and not limitation.

EXAMPLE 1 Delicious applies were mechanically peeled, cored, trimmed,and sliced. A batch of apple slices was placed in a glass impregnatorsimilar to that described above and covered with an aqueous solutioncontainin 60% sucrose, 0.1% ascorbic acid, and 1% citric acid. A vacuumwas applied above the surface of the liquid (29 in. Hg gauge pressure)and held until most of the air was exhausted from the apple tissue, i.e., until bubbling had substantially ceased. The vacuum was then brokenand the slices al owed to remain in the syrup for one to two minutes.The slices were then drained, packaged, and frozen at F.

After storage for about 1 month under refrigeration, the packages wereopened and the contents placed in the draft from an electric fan toexpedite thawing. After four hours the product was observed and tasted.It was found to have good color, good flavor, and firm texture. Pieswere made from the product using a standard technique. The apples in thefinished pie were found to have firm texture, good flavor, and goodcolor.

Control experiments The following experiments do not describe theprocedure according to this invention but are given to show the inferiorresults obtained according to prior art techmques.

(A) A pic was made using the same technique as for the pie in Example 1.Fresh apples were employed in preparing this pastry and were given a dipin a ueous sodium bisulphite (1,000 p. p. m. S02) before using toprevent oxidation.

(B) Another pie was made from frozen apples prepared in the usualmanner, i. e., fresh apple slices were di ped in aqueous sodiumbisulphite (2.000 p. p. m. S02), drained. st red for 8 hours to obtainmaximum penetration of sulphite, then frozen. The frozen slices werethen thawed and used to make the pie. The ap le fillin s of the ies werethen observed and tasted. The following results were observed:

Pie Texture Flavor I Color A oft Good--- Good. B Verysoft Low Good.

It is evident from the above that the apples prepared according to theinstant process are superior to the fresh fruit with regard to textureand superior to the usual frozen fruit with regard to both texture andflavor.

and tasted. The applev filling thereof had good color, good flavor, andfirm texture.

EXAMPLE 3 The process set forth in Example 1 was repeated. In this case,however, the syrup containing 50% sucrose and 0.1% ascorbic acid. Theproduct had good color, good flavor, and firm texture. The filling in apie prepared from the product had good flavor, good color, and bettertexture than when using fresh fruit.

Drainage tests A series of experiments were performed in order todetermine the amount of liquid formed upon thawing the frozen productsprepared according to this invention and to compare the results with theamount of drainage obtained with prior art processed.

(A) Apple slices were vacuum-impregnated in a solution containing 60%sucrose as heretofore described and the product frozen.

(B) Apple slices were vacuum-impregnated in a solution containing 40%sucrose as heretofore described and the product frozen.

(C) Apple slices were given a two-minute dip in aqueous sodiumbisulphite (2,000 p. p. 111. S02), stored for 8 hours at roomtemperature, and then frozen.

(D) Apple slices were vacuum-impregnated with an aqueous solution ofsodium bisulphite (500 p. p. 111. S02), then frozen.

In each case the frozen material was weighed and allowed to stand atroom temperature for 6 hours, then the material was poured on a screen,drained for 15 minutes, and the material on the screen weighed. By thismethod the amount of drain liquid was easily determined. The followingresults were obtained:

Loss in Weight due to drainage,

percent Experiment EXAMPLE 4 A series of frozen products were preparedto compare the processes of this invention and a prior art method. Ineach case, the raw material was sliced Gravenstein apples.

(a) One sample of the apple slices was processed in accordance with theprocedure set forth in Example 1. In this case, however, the syrupcontained 60% sucrose and 0.2% ascorbic acid. The products were packagedin cans and frozen at 10 F.

(b) Another sample of the apple slices was processed as follows: Theslices were dipped for 5 minutes in sugar syrup containing 60% sucroseand 0.2% ascorbic acid. The slices were then drained and filled intocans. The cans were then subjected to a vacuum of 29 inches of mercuryand sealed while under vacuum. The canned product was frozen and storedat l0 F.

(0) Another sample of the slices was sulphited by dippmg 2 minutes in asolution containing 2,000 p. p. m. S02 (added as NaHSOs and adjusted topH 3.0 with citric acid). The sulphited slices were drained, packaged incans and frozen and stored at 10 F.

Drainage tests The amount of drip or leakage in these products wastested by the following method: The products were defrosted by runningtap Water for 3% hours about the sealed cans. The defrosted slices werethen placed on an S-mesh screen and allowed to drain for 5 minutes,provision being made to catch the drainage liquid. The results are setforth in the following table. The amount of liquid which drained out ofthe products is expressed as the proportion of drainage liquid to totalweight of the product on a percentage basis.

Amount of drainage Product liquid,

Cent

Pie baking tests flavor.

EXAMPLE 5 A lot of fresh Newtown Pippin apples was peeled, cored, andsliced into twelfths. The slices were placed in a glass vessel andcovered with an aqueous solution containing 60% sucrose. A vacuum (29in. Hg) was applied above the surface of the liquid and held for 3minutes. The vacuum was then broken and the slices removed from thesugar solution and drained in a single layer on a screen.

A. Two #2 cans were each filled with 200 grams of the drained,syrup-impregnated apple slices. The cans were then sealed without addinganything, thus these cans contained only the drained, syrup-impregnatedapple slices.

B. Two #2 cans were each filled with 200 grams of the drained,syrup-impregnated apple slices. To each can was then added 200 ml. ofthe syrup used in the vacuum impregnation procedure, this amount ofsyrup being sufficient to cover the apple slices.

All four cans were then frozen in a refrigerator at F. and held at thistemperature for 3 days. The cans were then removed from the refrigeratorand allowed to thaw for 21 hours in a room maintained at 3540 F. Thecans were then opened and the contents of each was dumped onto a screen,provision being made ttl collect and measure the liquid exuding from thethawed s ices.

It was observed that products A-prepared by freezing the drained,vacuum-impregnated slicesdid not exude any liquid at all. Howeverproducts Bprepared by covering the vacuum-impregnated slices withsyrup-- exuded 221 ml. of liquid in one case and 222 ml. of liquid inthe duplicate experiment. Since only 200 m1. of syrup had been addedinitially, the experimental data indicate that 21 to 22 ml. of liquidwas extracted from the slices bly the osmotic effect of the sugar syrupsurrounding the s ices.

f The experimental results are set forth below in tabular orm:

Experiment No.

Conditions employed apples, ml.

though sucrose is preferred, other sugars commonly used for sweeteningfoods may be used. Thus one may employ dextrose, fructose, corn sugar,corn syrup, glucose, molasses, invert sugar, etc. Regardless of whattype of sugar is used, it should be present in approximately the rangeset forth above. Various agents may be added to the syrup to accomplishparticular purposes. Thus small amounts of ascorbic acid, from about0.1% to about 0.5%, preferably from about 0.2 to about 0.3%, may beadded to prevent or at least retard browning of the apples. Instead ofascorbic acid a sulphiting agent may be used for this purpose, thus onemay add sulphur dioxide, sulphurous acid, or any non-toxic, solubleinorganic sulphite or bisulphite such as sodium bisulphite, sodiumsulphite, potassium bisulphite, potassium sulphite, sulphites ofammonia, etc. In any case the concentration of the sulphiting agent,expressed as S02, should be from about 100 p. p. m. to about 500 p. p.m., preferably from about 200 p. p. m to about 300 p. p. 111. Bothascorbic acid and sulphiting agent may be added to the syrup in whichcase smaller amounts of each will be needed. A small percentage of salt(about .2% to 1%) is usually advantageous as increasing the effect ofthe ascorbic acid or sulphiting agent or their mixtures. In the case ofDelicious apples it is advisable to add some citric acid (0.5% to 1%) tothe syrup to give the apples a slight tartness which is lacking in thisparticular variety. If desired harmless food colors may be added to thesyrup to dye the apples any desired shade. Natural or synthetic flavorsmay be added to the syrup to give the apples any desired flavor. Infurther extension of this principle, the apples may be vacuumimpregnated with fruit compositions rich in sugar and natural flavoringconstituents, as for example, concentrated fruit juices. In such casethe fruit juice should be concentrated to such an extent that the sugarconcentration thereof is at least 40%, preferably from about 40% toabout 60%. A particularly desirable material in this category isconcentrated apple juice which has been prepared without significantlyaltering the natural flavor of the juice. One method for preparing sucha product is freeze concentration which involves subjecting the fruitjuice to temperatures below freezing and removing the ice from thetreated juice. Another method for preparing a suitable concentratedapple juice involves subjecting the apple juice to a first evaporationstep whereby the volatile essence is stripped from the juice. Theresidual juice and the essence are then separately concentrated,preferably under vacuum, and the concentrated residual juice and theconcentrated essence are then re-combined to give a highly flavoredconcentrate. The procedure of Walker and Talburt described in theirpatent application Serial No. 158,051, filed April 25, 1950, nowabandoned (abstract published in Patent Office Ofiicial Gazette, vol.654, page 324, January 1, 1952), may also be employed to produce asuitable apple juice concentrate. Their procedure involves stripping thevolatile essence from the juice, separately concentrating the residualjuice and the essence and then combining the concentrated essence,concentrated residual juice and fresh apple juice. An example ofpreparing a concentrate in this manner is set forth below:

44.6 gallons of fresh de-pectinized apple juice (l3.3 Brix) wassubjected to evaporation at atmospheric pressure to strip off about 25%of the juice. During this evaporation about 15 gallons of water wasadded to the juice by reason of the steam used to heat the juice bydirect contact. The stripped juice (40 gallons, 15 Brix) was thensubjected to evaporation under a pressure of about 1 in. Hg to yield7.475 gallons of juice concentrate (67.7 Brix). The volatile matterobtained in the stripping operation was distilled to obtain 0.495 gallonof concentrated essence (-fold concentrate). The juice concentratee,concentrated essence, and 5.1 gallons of fresh juice were mixed togetherto produce 13 gallons of an approximately 4-fold concentrate (45.7Brix).

If ascorbic acid or a sulphiting agent is not added to the syrup, thenit is desirable to give the apples a sulphiting dip prior to the vacuumimpregnation. For this purpose the apples are dipped into an aqueoussolution of sulphurous acid or any non-toxic, soluble inorganic sulphiteor bisulphite such as sodium bisulphite, sodium sulphite, potassiumbisulphite, potassium sulphite, sulphites of ammonia, etc. Theconcentration of sulphiting agent, expressed as S02, should be about1000 to about 2000 p. p. m. and the duration of the dip should be aboutone minute. In order to obtain thorough impregnation of the apple tissuewith the syrup it is necessary to peel the apples beforehand. Preferablythe apples are also cored and cut into convenient pieces, such as byslicing into sections ranging from halves to twelfths.

Although the process of this invention has been emphasized as atreatment prior to freezing, it is obvious that freezing is notessential. The impregnated apples can be used directly as a dessert orfor the making of pie or other food products.

The abbreviation p. p. 111. used herein means parts per million.

Having thus described my invention, I claim:

1. A method for preserving apples which comprises subjecting peeled,cored, and sliced apples to a 1-minute dip in a sulphiting bathcontaining about 1000 to about 2000 p. p. m. S02, removing the applesfrom the sulphiting bath, there being no storage period aftersulphiting, subjecting them to a vacuum, releasing the vacuum While theapples are immersed in a sugar solution v 8 excess sugar solution andthen freezing the drained, sugar-impregnated apples.

3. A method for preserving apples which comprises subjecting appleslices to a dip in a sulphiting bath containing about 1000 to about 2000p. p. m. S02, removing the apples from the sulphiting bath, there beingno storage period after sulphiting, subjecting them to a vacuum,releasing the vacuum while the apples are immersed in a sugar solutioncontaining about 40% to about 60% sucrose, removing the apples from thesugar solution, draining the sugar solution from the apples and thenfreezing the drained, sugar-impregnated apples.

References Cited in the file of this patent UNITED STATES PATENTS1,631,017 Crawford May 31 1927 2,209,889 Lachman July 30, 1940 OTHERREFERENCES The Freezing Preservation of Foods, 1943, by Tressler et al.,published by The Avi Publishing Co., New York, pages 285 to 287,inclusive.

U. S. Dept. of Agriculture Publication entitled Commercial Preparationand Freezing of Sliced Apples, August 1945.

Bauernfeind et al., article entitled Methods of Freezing Sliced Appleswith l-Ascorbic Acid, reprint from The Fruit Products Journal andAmerican Food Manufacture, Issue Vol. 26, Sept. 1946.

1. A METHOD FOR PRESERVING APPLES WHICH COMPRISES SUBJECTING PEELED, CORED, AND SLICED APPLES TO A 1-MINUTE DIP IN A SULPHITING BATH CONTAINING ABOUT 1000 TO ABOUT 2000 P. P. M. SO2, REMOVING THE APPLES FROM THE SULPHITING BATH, THERE BEING NO STORAGE PERIOD AFTER SULPHITING, SUBJECTING THEM TO A VACUUM, RELEASING THE VACUUM WHILE THE APPLES ARE IMMERSED IN A SUGAR SOLUTION CONTAINING ABOUT 40% TO ABOUT 60% SURCROSE, REMOVING THE APPLES FROM THE SUGAR SOLUTION, DRAINING THE SUGAR SOLUTION FROM THE APPLES AND FREEZING THE DRAINED SUGAR IMPREGNATED APPLES. 